NFS Clients See Pool's Available Space as Total Capacity

[7824c5a4]

Hello! First post on the forum!

I have an NFS share on a ~196TiB pool, and it has about 88TiB free. However, NFS clients are reporting the 88TiB number as the total capacity of the share, and that is causing issues on the client end.

Ive attached the output of df from the client, the NFS share settings, and the pool statistics. The machine is running Core 13.0-U3.1

Is this a ZFS accounting quirk, an issue with the client, or expected behavior? Is there any workaround?

Thank you!

 

[anodos]

What is the NFS client? What is output of df -h /mnt/ARCHIVE on the NAS?

 

[7824c5a4]

What is the NFS client? What is output of df -h /mnt/ARCHIVE on the NAS?

The clients are Ubuntu 14.04 and 18.04.
df -h /mnt/ARCHIVE spits out the following

 

[anodos]

What is output of zfs list -o space ARCHIVE?

 

[Arwen]

Yes, if I understand it correctly, it is a quirk of ZFS.

If you have snapshots or child datasets, the "SIZE" will be the dataset used+free space, not the total space in the pool.

If anyone has more complete, (or correct), information, please add to it.

 

[anodos]

Yes, if I understand it correctly, it is a quirk of ZFS.

If you have snapshots or child datasets, the "SIZE" will be the dataset used+free space, not the total space in the pool.

If anyone has more complete, (or correct), information, please add to it.

zfs/module/os/linux/zfs/zfs_vfsops.c at b93e39a9d40c5c53b8e6734169608d3d3ef0f449 · truenas/zfs

OpenZFS on Linux and FreeBSD. Contribute to truenas/zfs development by creating an account on GitHub.

github.com

Applications generally rely on statvfs (Linux) / statfs (FreeBSD) to report space. Ultimately, it all relies on:
```
dmu_objset_space(zfsvfs->z_os,
&refdbytes, &availbytes, &usedobjs, &availobjs);
```
Which in case of bytes counters means that response to statvfs is calculated from REFERENCED and AVAILABLE (though dmu_object_space() will also account for quota / reservation appropriately).

I have a feeling this user's issue is that the dataset in question has only 88 MiB available. I can't recall any applications that care about numbers other than `available` here.